Vehicle window glasses, and in particular, glasses in rear windows of vehicles, tend to collect moisture or cloud up with condensed dew. This is because the humidity often becomes higher in the interior of an automotive vehicle than on the exterior of the vehicle. In recent years, a ventilation system has been proposed which ventilates the interior of an automotive vehicle while the automotive vehicle is parked. The ventilation system includes a ventilation fan actuated by a solar cell when the interior of the automotive vehicle reaches a preselected temperature. Such a ventilation system is known from, for example, Japanese Patent Publication No. 59-51451.
However, since the ventilation fan of this known ventilation system is actuated according to the temperature of the interior of the automotive vehicle only when the automotive vehicle is parked and the engine of the automotive vehicle is stopped, it is impossible to actuate the ventilation fan so that the rear window glass is cleared if it is clouded with condensed dew while the automotive vehicle is traveling.